Abstract:

The saline-alkali land is one of the important reserve resources for food production in China. It is important to assess the overall impact of amelioration practices applied to saline-alkali soils from multiple aspects, including crop yield, soil amelioration and climate and environmental impacts. In order to investigate the effects of different soil conditioners on the yield of summer maize, soil carbon sequestration and N₂O emissions in saline-alkali lands in the lower reaches of the Yellow river, a field experiment was carried out in a light-moderate saline-alkali cropland located in Binzhou county, Shandong province, China. Seven treatments were set up in a summer maize field, namely blank control (CK), applying chemical fertilizers according to local practices (F), applying 50% of total nitrogen with manure (M), adding gypsum based on treatment F (G), adding microbial agents on the treatment M (MB), adding gypsum based on the treatment MB (MGB), and applying 70% total nitrogen with manure based on the treatment MGB (HMGB). Among the treatments, M and G were single conditioner treatments, and MB, MGB and HMGB were compound conditioner treatments. Results showed that: (1) application of conditioners had significant effects on both biomass and yield of summer maize compared with the local practice (F). For the crop yield, applying compound conditioners exhibited greater effects than single conditioners where both the number of grains per ear and the 100−grain weight significantly contributed to the increased crop yield under compound conditions. (2) Compared with the local conventional fertilization practice (F), the application of given soil conditioners significantly increased the proportion of 0.250−1.000mm macroaggregates in the soil by 10−20 percentage points, while reducing the clay content (<0.020mm) by 10−30 percentage points. Correspondingly, the contribution of the macro-aggregates to total soil organic carbon content increased by 3.0%−38.7% (0.250− 1.000mm), whereas the contribution of the clay fraction decreased by 3.3%−23.4% (<0.020mm). Notably, treatments applying with gypsum alone (G) and multiple conditioners exhibited significantly greater improvements in aggregate composition and their contributions to soil organic carbon compared to the treatment using organic fertilizer alone (M). (3) The cumulative N₂O emissions during the summer maize growth period for the representative treatments (CK, F, M, MGB) were between 443.8−1416.9gN·ha⁻¹. The treatments M and MGB showed significantly N₂O mitigation by 13.8% and 27.7%, respectively, compared with the treatment F. The results of this study indicated that the conditioner with high-amount manure + gypsum + microbial agent (HMGB) can be applied as a recommended choice for the saline-alkali soil for the multi−objective sustainable development, including increasing the crop yield and SOC, as well as mitigating N₂O emissions in the lower reaches of the Yellow river.

Key words: Saline-alkali amelioration, N2O emission, Soil conditioner, Soil aggregates, Soil carbon sequestration